1. Field of the Invention
This invention relates to hydrothermal growth of single quartz crystals. In particular, the invention is directed to a method of growing substantially stress-free quartz crystal stones on quartz crystal seeds.
2. Description of the Prior Art
Hydrothermal synthesis of quartz has been known for many years and has presently been refined to a point where a substantial amount of quartz used for frequency control applications today is synthetic or cultured quartz. In the commonly practiced commercial process for the hydrothermal synthesis of quartz, a vertical autoclave holds a supply of quartz nutrient in a bottom portion thereof, and is filled over half full with an aqueous solvent. The upper portion of the autoclave includes a plurality of planar quartz seed plates supported by a seed rack. The autoclave is sealed and then heated to increase the temperature and pressure sufficiently to cause the nutrient to dissolve into solution and thereafter be deposited on the seed plates. The autoclave is maintained in this condition for a number of days until stones of a desired size are grown on each of the seed plates in the seed rack.
The prior art discloses many ways for holding planar quartz seed plates in seed racks. In one known arrangement shown in U.S. Pat. No. 2,994,593 to Sullivan which is assigned to Western Electric Company, Inc. of New York, New York, clips of bendable metal are bent to contact the ends and the major faces of the seed plate and the distal portions of the clips are bent over horizontal supports of the seed rack. Another arrangement for holding seeds in the rack is to cut inwardly converging diagonal slots in the ends of the seed plate, insert wires therethrough and tie the wire to horizontal supports of the rack.
In the bendable clip arrangement, the growing quartz must grow around the bent portions that contact the surface of the seed plate. It has been found that in growing around such portions stresses are formed in the quartz stone resulting in dislocations and cracks which reduce the amount of usable quartz that can be cut from such a stone. When using the above-referred to slotting procedure, the forming of the slot itself will add stresses in the quartz plate which result in low yields. Also, such a procedure is tedious, requiring a substantial time to slot the seed plate in addition to the time required to wire the plates to the seed racks.